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1. Field of the Invention
The present invention relates to composite piling and more particularly to a piling apparatus that includes a helical anchor lower end portion to which a plurality of connectable sections can be added, each section having a hollow interior through which a drive member can pass, and each section being joined to another section at a joint that has a specially shaped fitting to be engaged by an enlarged portion of the drive member.
2. General Background of the Invention
Piling must often be installed in locations wherein a full size pile driving rig simply cannot be positioned. For example, if a building is having a settlement problem, piling must necessarily be driven below the building to support its lower most structural aspect, such as the lowest concrete horizontal section or slab.
It has been known in the art to cut holes through the slab of a building and then install a screw type anchor or screw type anchor piling system, in order to add support to an existing piling system that is already under the building. Once these additional piling have been placed, structural ties can be made between the building itself and the new piling.
Because pile driving equipment is not able to fit into the ground floor of existing buildings, a screw threaded piling or helical anchor is employed because it can be installed using a hydraulic rotary drive, for example. Such drive units are commercially available.
High capacity pile driving equipment is large and cumbersome to operate in confined areas. Conventional pile driving equipment can cause stress and fatigue on adjacent structures from weight and vibration.
Piles are used to support structures, such as buildings, when the soil underlying the structure is too weak to support the structure. There are many techniques that may be used to place a pile. One technique is to cast the pile in place. In this technique, a hole is excavated in the place where the pile is needed and the hole is filled with cement. A problem with this technique is that in weak soils the hole tends to collapse. Therefore, expensive shoring is required. If the hole is more than about 4 to 5 feet deep then safety regulations typically require expensive shoring and other safety precautions to prevent workers from being trapped in the hole.
It is known to provide a cylindrical foundation support element having an open lower end and which may be rotatably driven into the ground by virtue of the provision of an integral annular helix permanently affixed to the outer surface of the lower end of the support. The helix has an earth penetrating edge, and in conjunction with the cylindrical foundation defines an opening through which soil is allowed to pass into the chamber formed by the cylindrical wall of the foundation support. The opposite end of the cylindrical foundation support is adapted for releasable locking engagement to a drive element, which is used to rotate the support in a given direction, thus driving the support into the ground to a desired depth.
Langenbach Jr., U.S. Pat. No. 4,678,373 discloses a method for supporting a structure in which a piling beating a footing structure is driven down into the ground by pressing from above with a large hydraulic ram anchored to the structure. The void cleared by the footing structure may optionally be filled by pumping concrete into the void through a channel inside the pile. The ram used to insert the Langenbach Jr. piling is large, heavy and expensive.
Another approach to placing piles is to insert a hollow form in the ground with the piles desired and then to fill the hollow form with fluid cement. Hollow forms may be driven into the ground by impact or screwed into the ground. This approach is cumbersome because the hollow forms are unwieldy and expensive. Examples of this approach are described in U.S. Pat. Nos. 2,326,872 and 2,926,500.
Helical pier systems, such as the CHANCE(trademark) helical pier system available from the A. B. Chance Company of Centralia, Mo. U.S.A., provide an attractive alternative to the systems described above. As described in more detail below, the CHANCE helical pier system includes a helical screw mounted at the end of a shaft. The shaft is configured to draw the helical screw downwardly into a body of soil. The screw is screwed downwardly until the screw is seated in a region of soil sufficiently strong to support the weight which will be placed on the pier.
Many piling systems have been patented that include multiple sections, some of which are provided with screw anchors or helical anchors.
An early patent is the Gray patent entitled xe2x80x9cmetal Pilexe2x80x9d, U.S. Pat. No. 415,037.
The Stevens patent 1,087,334, discloses and incased concrete piling.
A method for installing anchoring or supporting columns in situ is disclosed in U.S. Pat. No. 3,354,657.
A piling that includes a cylindrical foundation support drivable into ground with a removable helix is disclosed in the Holdeman patent 5,066,168.
The Watts patent 3,422,629 discloses a construction support system and method and apparatus for construction thereof. A helical member is part of the apparatus.
U.S. Pat. No. 3,864,923 discloses a method and means for providing a pile body in an earth situs, including driving casing into situs to define a cavity of required depth. An auger positioned within the casing is rotatable in screwing direction to remove earth from defined cavity, and carries expansible cutter means rotatable with auger to enlarge cavity girth below inner end of casing. Earth removed from casing and cavity enlargement is replaced with different material, such as self-hardenable cement, to form pile body with load carrying enlargement at inner end of casing.
An earth auger is disclosed in U.S. Pat. No. 3,938,344 in which an auger shaft is provided with freely expansible and contractible rotary blades in such manner that said rotary blades may expand automatically when said auger shaft is rotated in the forward direction and may contract automatically when said auger shaft is rotated in the reverse direction. Also a method for driving piles and the like is disclosed which comprises the steps of positioning a pile or shoring adjacent to said auger shaft and above said blades, advancing said pile or the like into an earth bore excavated by said rotary blades, and filling said bore excavated by the rotary blades with mortar or the like.
The Turzillo patent 3,962,879 discloses a concrete pile or like concrete column formed in earth situs by rotating a continuous flight auger consisting or one or more sections into the earth to form a cavity of given depth; rotating the auger to remove augered earth from the cavity without removing the auger therefrom, and replacing the removed earth from the auger flights with fluid cement mortar, which hardens to form a column reinforced by the auger resultantly anchored in the same. A plurality of short auger sections may be connected together in succession during drilling to form a cavity of requisite depth by increments when low headroom conditions exist. A portion of the auger or a shaft portion without auger flighting thereon may also protrude above the earth situs for extension through water and the like and be filled with cementitious material which is allowed to harden. The method may also include first filling the auger shaft with the fluid mortar and allowing the same to harden in the shaft with a passage extending therethrough, and supplying more mortar through the passage to fill the cavity to form the column against backing of hardened mortar in the shaft.
The Vickars patent 5,707,180 discloses a method and apparatus for forming piles in situ. The xe2x80x98180 patent provides a method for making piles and apparatus for practicing the method. The piles may be used to support the foundation of a structure, such as a building. The method draws a soil displacer on a shaft down through a body of soil by turning a screw at the lower end of the shaft. The soil displacer forces soil out of a cylindrical region around the shaft. The cylindrical region is filled with grout to encapsulate and strengthen the shaft. The grout may be fed by gravity from a bath of grout around the shaft. The soil displacer has a diameter smaller than a diameter of the screw and may be a disk extending in a plane generally perpendicular to the shaft.
The present invention provides an improved method and apparatus for forming piles in situ. The apparatus of the present invention includes a lower helical screw anchor to which are attached a number of add on sections.
The present invention utilizes a screw threaded piling or helical anchor because it can be installed in confined areas, using smaller and more agile equipment (such as a Bobcat(copyright) type skidsteer equipped with a boom mounted hydraulic powered high torque planetary auger drive made by Eskridge, for example). Such units as these are commercially available.
In the preferred embodiment, each section is in the form of a hollow member (eg. thin wall pipe such as 0.188xe2x80x3 wall thickness or 0.125 wall thickness or Schedule 10 pipe)having a bore that receives a drive member or tool. The outer surface of each of the sections has soil displacing ribs that aid in pushing soil away from the sections as the pile apparatus is screwed down into the earth. The hollow bore of each of the sections receives an elongated drive member. The drive member is comprised of connectable sections wherein each of the connectable drive sections is about the same length as each of the pile sections. An enlarged drive member is provided at intervals as part of the drive member, the enlarged section registering with a correspondingly shaped joint that connects two pile sections together.
The present invention provides an improved method and apparatus for installing an in-situ pile apparatus.
A lower helical anchor lead unit with variable size helical discs is screwed into the soil, followed by a conically shaped cutting and soil displacing unit. This unit has strategically placed (2-4) triangular ribs for cutting and displacing soil outwardly away from the sectional pipe sections. This same unit will work as a pile cap for concrete that is poured into upper pipe sections. With this improved shape, it cuts the soil when rotated. The upper flat round plate of the conical will work as a bearing plate to the soil.
Once the conical unit has reached the soil, a drive tool will be attached to the helical lead unit, connected with a plastic or wooden dowel placed through the typical bolt hole.
A formed (thin wall 0.188xe2x80x3 or Schedulexe2x80x9410 0.125xe2x80x3) pile section that has squared ends is placed over the drive tool and bolted to the conical unit. Silicone caulking can be installed at each square section makeup joint to prevent water or mud from entering the pipe sections.
A hydraulic planetary drive unit is attached to the square drive tool. The hydraulic auger driver unit is engaged and the helical anchor, conical unit, attached pipe section(s) will be screwed downwardly into the soil. The hydraulic auger unit is then stopped and removed.
A second drive installation tool is bolted to the first. A second formed square sectional hollow form is placed over the drive tool and bolted. The hydraulic planetary drive unit is placed on top of the drive tool and the complete pile section is then screwed down into the soil until the top section reaches near ground level. This same process of installing drive tools and sectional hollow form units is repeated until the proper depth form has been reached (i.e. to satisfy the pile load requirements). As the complete pile unit is screwed down into the earth, the soil displacer ribs will push the soil outward away from the hollow pipe sections, creating less friction on the sections and therefore less torque.
With the proposed pile apparatus, the helical anchor will pull the hollow pipe forms down. At the same time the soil displacer ribs push the soil radially. This will allow the pile to penetrate deeper with less friction and a truer ft. lb. torque to capacity ratio. This method allows the pile to be installed as a point bearing pile, relying on the capacity of the helical discs that are screwed into the soil. In time, soil will reconsolidate around the larger diameter pipe forms which will develop a known friction capacity which will increase the overall pile capacity.
In one embodiment, a rod is provided that can be left with the pile section upon completion of installation to act as tensile rod or reinforcement for concrete that can be added to the internal bores of the various pile sections as connected end to end.
In another embodiment, plastic pipe sections can be added to the pile sections such as for example in water installations, the plastic pipe sections extending between the mud line and water surface. Other embodiments show various connectors for attaching the internal drive members together and for connecting the rod sections together.